The present invention relates to an apparatus for applying and/or spreading liquid or pasty substances for coating surfaces, in particular paints, varnishes and lacquers, on the surfaces of workpieces.
It is known to coat the surfaces of workpieces with liquid or pasty substances, for example paints, varnishes or lacquers, so as to protect them and/or to improve their appearance. To this end, the said substances are generally sprayed, rolled or poured onto the surfaces of the workpieces.
When rolling or pouring paints, varnishes or lacquers onto the surfaces of workpieces it is virtually impossible to obtain thin and very uniform coatings, in particular when the surfaces of the workpieces are uneven.
In the case of such surfaces, for example profiled surfaces, application of the coating substance by means of a spraying technique therefore remains the sole option for obtaining a somewhat more uniform coating. However, it is known even in the spraying technique that larger quantities of coating substance collect in small depressions on the surface than in the surrounding regions. This results in a locally thicker layer thickness when the coating has been applied. Particularly when the coating substance is a paint, this may result in a nonuniform intensity of color.
A further, generally known problem with the use of the spraying technique is the high consumption of coating substance and the environmental impact associated therewith, since during normal application by spraying, the process causes a not inconsiderable part of the coating substance to fall next to the workpiece to be coated.
It is therefore the object of the invention to apply and/or uniformly spread liquid or pasty substances for coating surfaces, in particular paints, varnishes and lacquers, on the surfaces of workpieces, in particular also on slightly profiled surfaces.
According to the invention, the object is achieved by an apparatus for applying and/or spreading liquid or pasty substances.
The apparatus according to the invention is ideally suitable for spreading liquid or pasty substances for coating surfaces, in particular, paints, varnishes or lacquers, which have been applied onto the surface(s) of the workpieces in the apparatus or in a preceding manufacturing step. Brush-like spreaders which are fitted to the circumference of spindles are used for the application and/or spreading. In the process, at least one of the spindles having the brush-like spreaders moves approximately parallel over the workpiece surface to be coated, while the workpiece is at the same time moved past the apparatus by a conveying device.
Surface profiles and slight unevennesses of the surface are absorbed by the elasticity in the brush-like spreaders to the extent that even here application and/or uniform spreading of the liquid or pasty substance takes place.
The practical use of the apparatus according to the invention resides in installing it as a coating station between a station for the substance application by means of a known technique, for example by means of a roller machine or by pouring, and a generally known and conventional drying station, for example a UV drying instalation, or in placing it as a coating station having integrated substance application directly in front of the drying station.
The arrangement of the brush-like spreaders fulfils the purpose of bringing the applied excess of coating substance into regions, such as depressions or profiled areas, and of spreading it there. A very uniform coating over the entire surface can thereby be achieved.
In a particularly advantageous manner, in one embodiment of the invention the spindles rotate about their own axis and at least two of the spindles are guided over the workpieces to be coated in a rotational movement running approximately parallel to the surface of the workpiece by a common rotor. A further rotating spindle, but which is fitted with its axis fixed in position, can be fitted at that end of the coating station which faces the drying station. This positionally fixed spindle with its own driving unit has the task of leveling the processing traces which may still be detectable and which the moveable spindles might have left behind on the surface to be coated.
In a further, very favorable embodiment, the brush-like spreaders are fitted on the circumference of the spindles at an acute angle to the axis of the said spindles. Because of the rotations of the spindles and the translatory movement of the workpieces past the apparatus, the friction of the bristles against the surface which is to be coated results in an equalizing movement of the bristles. This means that the arrangement of the bristles at an acute angle to the axis of the spindles can result in an oscillating movement of the bristles on the surface of the workpiece which is to be coated, which movement contributes to a very uniform spreading of the liquid or pasty coating substance. The coating substance is virtually xe2x80x9crubbedxe2x80x9d into the surface.
In addition, because of the oscillating movement of the brush-like spreaders and the virtually ideal spreading of the applied coating substance which is made possible as a result, a considerable quantity of this coating substance can be saved.
In a further, very advantageous embodiment of the invention, the brush-like spreaders are fitted on disk-like holders which can be plugged onto the spindles. They can be pushed onto the spindle in alternating fashion with one or more spacer disks in a manner secure against rotation. The individual elements can then finally also be clamped with respect to one another on the spindle by means of a fastening device. In this case, the use of angle-equalizing disks also makes it possible for different angular positions of the bristles with respect to the axis of the spindle to be realized in a simple manner.
This very flexible design of the coating station can thus be adapted rapidly and simply to virtually any desired task and any coating substance. Thus, for example by a change in the distance between the brush-like spreaders, the installation can be adapted without great outlay to the present situation, for example to the viscosity of the coating substance used or to the condition of the surface of the workpieces to be coated. The advantages obtained thereby in the saving on set-up time, manufacturing sequence and ultimately in the logistics are obvious.
However, the arrangement of the brush-like spreaders on the disk-like holders provides yet further advantages, particularly also in the handling of the parts. Thus, the disk-like holders together with their brush-like spreaders are considerably more easy to handle during storage and dispatch and are damaged less frequently than complete spindles fitted with brush-like spreaders.
The advantageous properties of the apparatus according to the invention are also further assisted in that the rotor, the moveable spindles and the at least one positionally fixed spindle can be set completely independently of one another in their rotational speed and direction of rotation.
If the coating station is used with an integrated substance application, as one of the advantageous refinements of the invention envisages, the liquid or pasty substance for coating surfaces can be picked up by the revolving brush-like spreaders on that side of the spindles which faces away from the surfaces to be coated.
In order to avoid workpieces which are to be coated from tilting and rising up between the spindles having the brush-like spreaders, in a particularly advantageous embodiment of the invention, holding-down clamps can be provided between the spindles. In a particularly favorable design, these holding-down clamps, which can partly also be moved together with the moveable spindles, have beveled or rounded regions on their edge regions facing the spindles.